A variety of gas turbine power plant designs have been employed in the past. In a representative example, fuel, e.g., natural gas, is fed from a fuel supply into a plurality of fuel manifolds, each fuel manifold communicating with a plurality of fuel lines, each of the fuel lines in turn communicating with a respective combustion canister. The combustion canisters are arranged relative to the turbine such that exhaust from burning the fuel drives the turbine, in a manner which is abundantly well known in the art.
Valves have been employed to control the rate of flow of fuel into each of the combustion canisters, e.g., by providing a valve in each fuel line connecting a combustion canister to a fuel manifold. By providing such valves, it has been possible to provide different flow resistances in different fuel lines, e.g., to make it possible to adjust the fuel in each of the combustion canisters, e.g., such that fuel flow to each combustion canister may be maintained at values which are the same as or substantially the same as those in the other combustion canisters. For example, even in cases where different fuel lines are connected to a fuel manifold at locations which are different distances from a fuel inlet connecting the fuel supply to the fuel manifold and/or through flow paths of differing geometries, uniform fuel/air mixtures can be provided to each of the combustion canisters by adjusting the respective valves (for example, by creating greater valve flow resistance in fuel lines which are closer to the fuel inlet and/or which are connected through a flow path geometry having lower resistance).
One valve design which has been particularly useful in such a gas turbine power plant system is depicted in FIG. 1. Referring to FIG. 1, the valve includes a valve body and a bonnet, the valve body including a valve stem and a translator. The valve body includes a bonnet receiving region in which at least a portion of the bonnet is positioned, and a flow channel 100.
The valve is connected in a well known manner to a flanged inlet pipe (not shown) on one side of the valve and a flanged outlet pipe (not shown) on the other side of the pipe by connecting a first circumferential flange 101 on the valve body to a circumferentially flanged inlet pipe such that a conduit defined by the inlet pipe communicates with the flow channel 100, and connecting a second circumferential flange 102 on the valve body to a circumferentially flanged outlet pipe such that a conduit defined by the outlet pipe also communicates with the flow channel 100. Accordingly, the conduit defined by the inlet pipe communicates with the conduit defined by the outlet pipe through the flow channel 100 which passes through the valve.
The valve stem includes a cranking portion 110, a cylindrical portion 111 and a bell-shaped portion 112. The translator includes a translator stem portion 113 and a flow regulating portion 114. The translator stem portion 113 has external threads which engage internal threads on a threaded insert 115 which is welded to the inside of the bell-shaped portion 112.
The cranking portion 110 of the valve stem can readily be engaged with a manual cranking tool in order to rotate the valve stem about its axis (i.e., the valve stem rotates axially without moving translationally), thereby causing the translator to move in a direction along the axis of the valve stem by virtue of the threading of the external threads of the translator stem portion 113 on the internal threads of the threaded insert 115. As a result of such motion, the flow regulating portion 114 of the translator moves relative to the flow channel 100 between a position (see FIG. 2) where the flow regulating portion 114 is in contact with the bottom (in the orientation shown in FIG. 2) surface of the flow channel 100, i.e., the surface which is opposite to the valve stem (maximum flow obstruction) and a position where the flow regulating portion 114 is retracted (upward in the orientation shown in FIG. 2) out of the flow channel 100 (minimum flow obstruction).
Such a valve stem is referred to herein as a “non-rising” valve stem, because operation of the valve can be achieved without the valve stem rising or falling within the valve body (rising or falling referring to moving upward or downward in the perspective depicted in FIG. 1). That is, the valve can be operated by rotating the valve stem about its axis without moving the valve stem translationally.
Such a valve has been effective as a flow control valve in which the position of the translator can be set by rotation of the valve stem to provide a desired flow resistance, and the translator remains in that position for the duration of the useful life of the valve. As such, a plurality of such valves can be manufactured, and then each of the valves can be set at a different flow resistance to provide the varying flow resistances required of a set of valves in the fuel lines extending from different positions along a fuel manifold. Such valves are sometimes referred to as “set and forget” valves.
Despite such valves and the myriad systems in practice, there is an ongoing need for systems which generate power more efficiently, more safely and with fewer environmental side effects (e.g., lower emission levels and/or less hazardous emissions).